1. Field
Embodiments of the present invention relate to a non-contact type of information apparatus that reads and writes information in a non-contact fashion and, in particular, to one of a radio frequency identification (RF-ID) tag and a non-contact type IC card, e.g., that accumulates a value detected by a sensor detecting one of a physical quantity and a physical state.
2. Background
An active battery-powered radio frequency (RF) identification (ID) tag is attached to a commercial product or a person. The active battery-powered RF-ID tag transmits an RF signal on a predetermined frequency related to the ID and information on the commercial product or the person. The RF signal is then read by a reader apparatus. A computer or the like may process the read information and thus monitor and manage the circulation of the commercial product and the behavior of the person. The active-type battery-powered RF-ID tag, in comparison with a passive RF-ID tag that needs to receive power from a reading/writing apparatus, has a relatively large communication coverage area and is practicable.
The RF-ID tag, having a sensor detecting a physical quantity in a surrounding environment, accumulates data of a value detected by the sensor. A reading/writing apparatus reads the data from the RF-ID tag to collect detected value data together with the identification (ID).
Japanese Patent Laid-Open No. 2000-113130A publicly disclosed in Japan dated Apr. 21, 2000 discusses an IC tag detection system operating at low power consumption. An IC tag used in the system includes a communication circuit, a controller, a power source for supplying power from a battery to the system, and a time measurement circuit. The IC tag performs a transmission operation at each predetermined set time. A plurality of IC tags having different set times are arranged. A detector device communicates with each of the IC tags and detects the presence or absence of each IC tag in response to communications with the IC tags. The detector device having a communication circuit determines the presence or absence of reception at each time set for each IC tag. Since no enquiry is made from the detector device, the IC tag is free from useless responding and power consumption.
Japanese Patent Laid-Open No. 2001-251210A (corresponding to U.S. Pat. No. 6,922,402B1) publicly disclosed in Japan dated Sep. 14, 2001 discusses a method of implementing a frequency lock in which each of transmitters on both nodes needs no separate reference oscillator in a duplex link. In the implementation method of the frequency lock, a carrier frequency of a transmitter is tuned using information relating to a receiving frequency in a full-duplex link so that transmission frequencies on both nodes are locked in the link. An offset in the carrier frequency of a first transmitter is detected as an offset in a corresponding second receiver. The second receiver shifts the carrier frequency of the corresponding transmitter in response to the detected offset, and notifies the first transmitter of the detected offset. The offset detected in the first receiver thus corrects the carrier frequency of the corresponding transmitter.
Japanese Patent Laid-Open No. 2006-72727 laid open in Japan dated Mar. 16, 2006 discusses a non-contact type IC tag having a sensor. In the non-contact type IC tag having the sensor, a clock set signal output to a clock from a controller is output via an electronic circuit including a tag effective period determiner between the controller and the clock. The tag effective period determiner causes the controller to output a tag effective period setting signal. With the tag effective period determiner arranged between the controller and the clock, the non-contact type IC tag having the sensor disables the operation of the clock during a tag effective period. In this way, without using encryption and a keyword, the non-contact type IC tag having the sensor makes it extremely difficult to alter results of measurement, and is also recycled.